Which of the following propositions are so related that they cannot both be false, although they may both be true?

1.Some cars are polluting vehicles

2.Some cars are not polluting vehicles

3.All cars are polluting vehicles

4.No cars are polluting vehicles

A3 & 4 only

B1 & 2 only ✓ Correct

C2 & 3 only

D1 & 3 only

Correct answer: (B) 1 & 2 only

Explanation

Statement 1 and Statement 2 can both hold together yet never both fail together.

Statement 1 is the particular affirmative I: Some cars are polluting vehicles.

Statement 2 is the particular negative O: Some cars are not polluting vehicles.

An I and an O with the same terms are subcontraries.

Subcontraries cannot both be false, though both may be true, exactly the relation described.

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